Firstly, this centers on two assumptions: - Optimus said to Megatron in the first film: “You left me no choice, brother.” This would mean they were kindred, the Cybertronian Cain and Abel who took their rivalry to new heights. Some would disagree, saying they were just brother Cybertronians, but I hold to them being blood-brothers as it makes for a new and great dimension to their relationship, rather than G1’s rebel leaders (Megatron a gladiator and Optimus a record clerk?). It also presents the Transformers war as a blood feud, which Earth gets caught up in. - Sentinel Prime was leader of the Autobots before Optimus, as was explained in DOTM. This would make Sentinel a direct descendant of Optimus Prime, from before the war began. This would mean he was possibly a father Optimus Prime and by the above conection Megtron too, and probably sired them both (I use “sired” as in the genealogical sense, not physical). What I’m getting from this is: Sentinel Prime let a war between his own sons take place, sold out one son to the other to save Cybertron, had one son set up to be killed and deposed his other, and then got killed by them both? Yeesh. This is the stuff that the Borgias and Corleones are made of. If you think about it, this is Shakespearian in proportion, akin to THOR’s family saga (Odin, Thor and Loki). And like much of DOTM, it could have been handled in a more appropriate and awesome manner. Less humorously, it looks like Primes make for great villains: Megatron, the Falllen and Sentinel Prime are all Primes in some form. It would make sense, looking at the familial connections, for the new villain in TF4 to also be another sort of Prime.